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14a - HSPF Modeling: Hydrology

14a - HSPF Modeling: Hydrology. Virginia Tech Biological Systems Engineering Department 2013 DEQ TMDL Workshop. Model Development Process – Become familiar with the model development process and hydrology model development specifically

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14a - HSPF Modeling: Hydrology

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  1. 14a - HSPF Modeling: Hydrology Virginia Tech Biological Systems Engineering Department 2013 DEQ TMDL Workshop

  2. Model Development Process – Become familiar with the model development process and hydrology model development specifically Preliminary Tasks – Identify tasks performed in preparation for hydrology model development Hydrology Model Construction - Review steps taken in the construction of an HSPF hydrology model Hydrology Model Calibration & Validation – Discuss these essential steps in HSPF hydrology model development Overview/Objectives

  3. Model Development Process

  4. Model Development

  5. Model Development

  6. Preliminary Tasks

  7. Surrogate Watershed Use • Use only if there is no suitable stream gage in the study watershed • Suitability: • Flow Gage period of record • Close proximity to study watershed • Similar area, slope, land use, & soils composition • Develop HSPF model for surrogate, calibrate, & validate • Transfer hydrology parameters to study watershed model

  8. Compare and Contrast

  9. Modeling Periods Selection Sum of monthly ave. flows (cfs) • Dependent on data availability (flow and climate data) • Avoiding “extreme” years, identify 5-year period (consecutive) with high and low seasonal flows

  10. Storms Selection • About 30 storms for calibration, and another 30 for validation • Flow response to precipitation • Seasonal distribution of storms

  11. Flow Partitioning • Measure of stream flow contributed by baseflow • Target range is based on observed data • Used during hydrology calibration

  12. Hydrology Model Construction

  13. HSPF Hydrology Simulation

  14. Hydrology-Building Input • Meteorological Data • UCI File - Parameterization • PWATER & IWATER: PLS and ILS • HYDR: RCHRES and F-TABLES • Hydrologic Calibration/Validation

  15. Key Input Parameters – PWATER

  16. Source: EPA BASINS Technical Note 6 Key Input Parameters – PWATER

  17. PLS • Flags (toggles) • Parameters • State Parameters • Monthly-variable • parameters

  18. ILS • Flags (toggles) • Parameters • State Parameters

  19. RCHRES • GEN-INFO Block • HYD-PARM Blocks • Individual & grouped values

  20. FTABLES

  21. Permitted Discharges & Withdrawals • EXT SOURCES Block • WDM time series • VPDES discharges and withdrawal (observed data)

  22. Hydrology Model Calibration & Validation

  23. Model Calibration • Definition • Adjustment of model parameters to improve accuracy of model results • Objective • Ensure that model parameters accurately represent watershed conditions • Criteria • Model results should “match” observed data • Parameter values should be “consistent” with watershed characteristics

  24. Model Validation • Definition • Assess model performance for periods other than the calibration period • Objective • Ensure that calibrated parameters are appropriate for time periods other than the calibration period • Criteria • Model results should “match” observed data

  25. Calibration/Validation Progression • Hydrology • All components depend on this • Erosion/Sediment (if necessary) • Water Quality Calibration Validation

  26. Hydrology Model Calibration Sequence • Storms • Seasonal Water Balance • Annual Water Balance

  27. Remember - Rainfall Data are not Perfect • Check accuracy of record • Does the rainfall data agree with the observed data • What type of gage was used • Who maintains the instruments and the data • Are the data adequate • Enough stations?

  28. HSPExp • Decision Support System for Hydrology Calibration • DOS based (computer savvy) • Does not: • Help with snow pack • Assist in erosion calibration • Assist in water quality calibration • URLhttp://water.usgs.gov/software/hspexp.html • EPA Technical Note 5Using HSPEXP with BASINS/NPSMhttp://www.epa.gov/waterscience/basins/tecnote5.html

  29. Calibration/Validation Criteria • Total volume • Error in total runoff for the calibration period • Low flow recession • Error in the mean of the low-flow recession rates • 50% lowest flows • Error in the mean of the lowest 50% of the daily mean flows • 10% highest flows • Error in the mean of the highest 10% of the daily mean flows • Storm peaks (not volumes) • Error in flow peaks for selected storms • Seasonal volume • Seasonal volume error (summer June-Aug, winter Dec-Feb) • Summer storm volume • Error in runoff volume for selected summer storms

  30. Calibration/Validation Criteria

  31. Calibration Runs

  32. Hydrology Calibration

  33. Hydrology Calibration

  34. Hydrology Calibration

  35. Hydrology Calibration

  36. Hydrology Calibration

  37. HSPF Exercise • Open file HSPF_Exercise.uci • Using the PWAT-PARM2block, identify the overland flow plane length (LSUR) for PLS 121 (Pasture Land Use in Subwatershed 2). • Using the MON-INTERCEP block, identify the interception storage capacity at the beginning of March on all pasture land. • What is the Manning’s coefficient being used in the model for roads, driveways, and similar surfaces?

  38. HSPF Exercise - Answers • Open file HSPF_Exercise.uci • Using the PWAT-PARM2block, identify the overland flow plane length (LSUR) for PLS 121 (Pasture Land Use in Subwatershed 2). 380 ft. • Using the MON-INTERCEP block, identify the interception storage capacity at the beginning of March on all pasture land. 0.13 inch • What is the Manning’s coefficient being used in the model for roads, driveways, and similar surfaces? 0.08 (unitless)

  39. Questions?

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